The former UBS trader who is accused of unauthorised deals that cost the Swiss bank $2.3 billion in losses will spend the Christmas holiday in jail after a London court gave him more time to consider his plea after changing his legal team, reports said.

Lawyers representing Kweku Adoboli, who worked as a director of exchange-traded funds, said he could not enter a "proper and meaningful" plea because he was unhappy with the guidance he had received from a defence team that he dropped last week, news services said.

His next hearing is on 30 January; he must enter a plea over two charges of fraud and one of false accounting.

A report by Reuters, quoting new defence lawyer Paul Garlick, said: “I am certainly not satisfied that he has received adequate legal advice.” He added that Adoboli would plead not guilty, if pressed by the court to make an early decision.

The saga has rocked Switzerland’s largest bank. Former chief executive Oswald Grübel resigned in September, eventually replaced by Sergio Ermotti, a senior UBS executive. Commentators at the time, however, did not think that UBS’s wealth management business would be damaged by client pullouts in the wake of the loss revelation.

UBS has signalled it intends to significantly reduce the risk exposures at its investment bank and increase its focus on wealth management.